1H nuclear magnetic resonance spectroscopy (NMR) at 750 MHz was used to measure H/D fractionation factors and the temperature-dependence of hydrogen exchange in the catalytic triad of chymotrypsinogen. The results indicate that the strength of hydrogen bonding increases markedly on going from the resting state of the catalytic triad (pH 9), consisting of carboxylate - H-imidazole ... hydroxyl, to a low pH (pH 3.5) model of the tetrahedral intermediate, consisting of carboxylate - H-imidazolium-H ... hydroxyl. It was possible to determine properties of the hydrogen bonds in both the aspartate-102 -- histidine-57 and histidine-57 -- serine-195 diad in this model of the tetrahedral intermediate.